Strange! Nothing jumps out at me as being an obvious problem with your setup. I'm doing something similar, though instead of rtlamr2mqtt (which I didn't know about) I have a bash script run via cron that parses rtlamr output via jq and pipes that to mqtt (mosquitto), but there's very little to it. I know the energy dashboard setup is picky about the energy recording entities.

Mine looks like:

state_class: total_increasing
unit_of_measurement: ft³
device_class: gas
friendly_name: Gas Meter

The name of the entity is sensor.gas_meter and the state is currently 113812 as an example.

Might be worth reading through GitHub issues for rtlamr2mqtt, including closed ones, if you haven't already. Or maybe a hass restart? Can't think of anything else.